Recent changes in the healthcare system necessitate that health consumers and patients play a more active role in the management of their health. Older adults, in particular, face many challenges in today's health care environment in terms of the increased complexity of health care systems and the proliferation of health information from numerous and diverse sources. Health literacy skills are needed for communication with healthcare providers, reading and understanding health information, medication compliance, using medical devices and making decisions about treatment options. Health literacy is lower among people aged 7 65, especially ethnic minorities and those with lower socio-economic status. Current measures of health literacy are limited in scope and inadequate in diagnosing specific literacy-related problems. The overall objective of this study is to develop and validate a health literacy instrument for older adults employing state-of-art computer-adaptive testing methods and technology. The first aim is to develop a comprehensive framework for identifying and measuring the core competencies that older adult consumers need to understand, access and use health related information and services. Towards that end, we will engage in a series of formative research activities including a systematic review of existing measures, convening an expert panel on health literacy and performing a series of cognitive task analyses on health related activities (e.g., glucose testing). This will contribute to the development and implementation of conceptual knowledge and numeracy modules. The prototype modules will be implemented as adaptive tests based on measurement decision theory. A preliminary study with 15 older adults at varying levels of health literacy will be conducted to develop testing norms. The data will be analyzed by investigators and scrutinized by members of the expert panel. On that basis, we will revise the 2 modules and subject it to a larger validation study with 2 groups of older adults: 1) ages 60-74 and 2) 75-85. A primary strength of this application is that we are addressing an issue of considerable and growing importance using a theoretically-grounded framework that greatly expands the scope of health literacy assessment. A comprehensive health literacy framework as described in this application can be used to support research on health literacy, develop screening tools for clinicians and tailor health education materials for older adult adults at varying levels of literacy. Public Health Relevance: literacy problems exist to a large extent because health information and services systems are unfamiliar and complex, which makes their effective utilization difficult for most people, especially for older adults. We are proposing to develop a health literacy assessment tool based on a comprehensive framework. The tool has the potential to be used to support research on health literacy, develop screening tools for clinicians and tailor health education materials for older adult patients and consumers at varying levels of literacy.